LIFE HISTORY TRAITS OF THREE MORPHS OF MELANOIDES TUBERCULATA (GASTROPODA: THIARIDAE), AN INVADING SNAIL IN THE FRENCH WEST INDIES

The life history traits of three morphs of the parth-enogeneticsnail Melanoides tuberculata were studied under laboratory conditions.Differences in growth size, mortality and reproduction rateswere observed between morphs, indicating adaptation to differentdemographic strategies. These results are discussed in relationto the invasion of the species which occurred in Guadeloupeand Martinique. (Received 24 February 1992; accepted 30 April 1992)     

STARVATION, DESICCATION AND USE OF ALLOSPERM IN THE HERMAPHRODITE FRESHWATER SNAIL BIOMPHALARIA GLABRATA (GASTROPODA: PULMONATA)

Pairs of albino and pigmented snails were used to test the hypothesisthat the hermaphrodite freshwater gastropod Biomphalaria glabratawas able to conserve and use allosperm, despite periods of desiccationand starvation. In laboratory experiments, lots of twenty snailswere subject to 0, 5, 10, 15 AND 20 days starvation; similarlots of 20 snails were subjected to 0, 2, 4, 6, 8, 10 weeksof desiccation at R.H. 100%. After all periods of starvationand desiccation, albino parents were still producing significantnumbers of pigmented offspring, suggesting preferential cross-fertilizationusing stored allosperm. (Received 30 September 1993; accepted 23 December 1993)     

POPULATION STRUCTURE OF BIOMPHALARIA GLABRATA, INTERMEDIATE SNAIL HOST OF SCHISTOSOMA MANSONI IN GUADELOUPE ISLAND, USING RAPD MARKERS

Nine populations of the snail Biomphalaria glabrata, sampledin 1992 and in 1994 in the Guadeloupean focus of schistosomiasis,were studied using random amplified polymorphic DNA (RAPD) markers.The detected polymorphism was low with 11 polymorphic markers.A canonical analysis of the genetic polymorphism showed a significantand large differentiation between the nine populations studiedin a restricted area of 45 km². A Mantel t–test indicateda significant correlation between the genetic differentiationand the geographical distance. A significant but smaller differentiationbetween a northern and southern group was also observed usingcanonical analysis. A comparison over time has been done. Corresponding author: A. Théron. Laboratoire de Biologie Animale,UMR 5555 CNRS, Centre de Biologie et d'Ecologie Tropicale et Méditerranéenne,Université, 52 Av. de Villeneuve, 66860 Perpignan Cedex,France. Tel: +33 4 68 66 21 83 Fax: +33 4 68 66 22 81 E-mail:theron{at}univ-perp.fr (Received 26 October 1998; accepted 30 December 1998)     

MANIPULATION OF BIOMPHALARIA GLABRATA (SAY) (GASTROPODA: PLANORBIDAE) HAEMOCYTES IN VITRO

The propensity of molluscan haemocytes to clump irreversiblyupon mixing in suspension, together with their strong adherenceto many substrates, compromises many efforts to obtain plasma-freeor treated cells for subsequent use in experimental protocols.An anti-clumping buffer developed for use with haemocytes fromthe gastropod Lymnaea stagnalis was tested for its effectivenesswith cells from Biom-phalaria glabrata. While we were unableto obtain sufficient numbers of viable haemocytes for subsequentexperimentation after centrifugation, this divalent cation-chelatingbuffer induced rounding of adherent cells monolayered on glass.Thus, cells washed in physiological buffers could subsequentlybe retrieved as monodispersed suspensions. Such haemocytes retainedsome phagocytic activity, with levels of uptake improved whencells were held in buffer with excess divalent cations beforeaddition of target particles. (Received 7 September 1992; accepted 6 January 1993)     

DEMOGRAPHY AND GROWTH OF ANOMALOCARDIA BRASILIANA (GMELIN) (BIVALVIA: VENERIDAE) IN A MANGROVE, IN GUADELOUPE (FRENCH WEST INDIES)

Anomalocardia brasiliana is a venerid clam which lives slightlyburrowed in sandy mud of shallow water environments throughoutthe Caribbean region. A 42-month study in a mangrove lagoonshows that the population is characterised by a variable recruitmentpattern on a year-round basis but with infrequent success. TheGompertz function gives a good estimation of growth. The weight-sizerelationship shows alternative isometric and subdeterminantallometric growth periods. A short life and variable demographicstructure seem to be characteristics of lagoon as well as oftropical populations. (Received 5 February 1990; accepted 26 July 1990)     

PATTERNS OF SEXUAL ROLES ADOPTED BY THE SCHISTOSOME-VECTOR SNAIL BIOMPHALARIA GLABRATA (PLANORBIDAE)

Relatively little is known about the mating behaviour of hermaphroditefreshwater snails, many of which transmit the Schistosoma trematodesamong humans in developing countries. Knowledge of the breedingbiology of these snails could help in the design of schistosomecontrol programmes, as well as possibly contributing to ourunderstanding of the evolution of simultaneous hermaphroditismin animaL. Here we describe an experiment investigating thepatterns of sexual roles adopted by the Schistosoma mansoni-vectotsnail, Btmphalaria glabrata. During observations on groups offreely interacting snails, no individuals copulated significantlymore often in the male than in the female role, or vice versa.Only one individual showed a pattern of alternating sexual rolesover successive matings that differed significantly from a randomsequence of roles. There was no evidence for reciprocal copulationwith one particular partner, either between consecutive matings(unless they were temporarily isolated from other snails) orbetween non-consecutive matings (separated by copulations withother conspccifics). We discuss these results in the contextof sex allocation and ESS mating strategy theories. ^*Present address (or correspondence 1 G VERNON. Bioscan (UK).Standingford House, Cave Street, St. Clements, Oxford OX4 IBA. (Received 5 October 1995; accepted 6 November 1995)     

THE EFFECT OF CONSTANT TEMPERATURES ON THE HATCHING OF EGGS AND SURVIVAL OF THE FRESHWATER SNAIL BIOMPHALARIA GLABRATA (SAY)

SUMMARY

The incubation period and percentage hatching of eggs of pigmented and unpigmented Biomphalaria glabrata at constant temperatures were investigated in the range 14 °C to 34 °C. In order to determine the influence of extreme temperatures on adult snails, specimens of the same species were exposed to 0 °C and 40 °C for selected time periods. The results indicate that sustained temperatures below 16 °C and above 32 °C are detrimental to the development and hatching of B. glabrata embryos. The optimum temperatures for incubation period and hatching differ from each other. As far as temperature is concerned, this foreign snail species should be capable of successfully colonizing the warmer parts of southern Africa.     

DEVELOPMENT OF ACCESSORY SEXUAL ORGANS IN BIOMPHALARIA GLABRATA (PLANORBIDAE) IN RELATION TO TIMING OF INFECTION BY SCHISTOSOMA MANSONI: CONSEQUENCES FOR ENERGY UTILIZATION PATTERNS BY THE PARASITE

The growth rates of ovotestis and individual accessory sexualorgans (ASO) of Biomphalaria glabrata snails were studied forcontrols and for immature and mature snails infected with Schistosomamansoni. The infection of immature B. glabrata strongly delaysgrowth of the ovotestis and inhibits the development of theaccessory sexual organs. There is no significant differenceup to 2 weeks post infection in the volume of the ovotestisand the ASO between mature infected B. glabrata and controlsnails. From 3 to 4 weeks post infection there was a reductionin the volume of the ovotestis and the ASO of infected matureB. glabrata; then growth of the ovotestis, albumen gland andfemale organs was stopped, but the effect of infection was lessconsistent for the male organs. For a parasite, immature andmature snails have to be considered as two different resourceenvironments, each having at infection time a particular patternof resource allocation, towards growth for juvenile and towardsreproduction for adult snails, changing the possible energyutilization patterns which can be used by the trematode. (Received 29 January 1993; accepted 22 April 1993)     

TAXONOMIC IMPLICATIONS OF EXTERNAL POLLEN MORPHOLOGY TO VERNONIA (COMPOSITAE) IN THE WEST INDIES

External pollen morphology of 39 species of West Indian Vernonias was examined by light and scanning electron microscopy in conjunction with a systematic revision of these species. There were three distinct types of pollen: Type A: subechinolophate, tricolporate grains with prominent spines; Type B: echinolophate, tricolporate with expanded germinal furrows and coincident polar muri; Type C: echinolophate, tricolporate grains with prominent polar lacunae. Pollen grains intermediate between the major types were found in several species. These same species had very distinct and atypical megamorphologies. In general, pollen types were found to correlate well with classification based on megamorphological characters, particularly at the infrageneric level, and to provide confirmation of subsectional assignments in the genus.     

GROWTH AND DEMOGRAPHY OF POPULATIONS OF BIOMPHALARIA PFEIFFERI (GASTROPODA, PLANORBIDAE) IN THE LABORATORY

The growth and demography of the freshwater snail Biomphalariapfeifferi, an intermediate host of the parasitic worm Schistosomamansoni in Eastern Zaire, were investigated in the laboratoryunder two conditions of crowding. Both individual and populationgrowth were depressed by crowding. Crowding reduced growth rateand all the variables and parameters related to reproduction(fecundity, instantaneous birth rate, net reproduction rate),but did not affect maximum size, survivorship, instantaneousdeath rate and life expectancy. The mechanism involved in theseeffects is likely to be exploitation competition for especiallyprofitable food items such as diatoms. (Received 10 November 1986;     

DISTRIBUTION OF THE SCHISTOSOME VECTOR SNAIL, BIOMPHALARIA STRAMINEA (PULMONATA: PLANORBIDAE) IN HONG KONG

Biomphalaria straminea (Dunker) is a snail intermediate hostof Schistosoma mansoni Sambon which has invaded Hong Kong inrecent years from its home range in Brazil. This study examinesits distribution pattern in terms of habitat type and hydrologicalfactors. The data revealed very strong colonizing power, bothin terms of number of sites occupied as well as numerical dominanceat these sites. An inability to colonize lotic habitats mayhave been related to low levels of dissolved minerals and nutrientsbut the effect of current speed on colonization has yet to beresolved. Principal component analysis revealed that hydrological factorsimportant for colonization included high levels of dissolvedcalcium, magnesium, iron, chloride, total nitrogen, sulphateand phosphate. pH had only a secondary effect. The significanceof these findings is discussed with special reference to thelikelihood of introduction of B. straminea elsewhere, and possiblemanagement strategies. (Received 16 December 1988; accepted 12 February 1989)     

HAEMOCYTES OF THE FRESHWATER SNAIL VIVIPARUS ATER (GASTROPODA, PROSOBRANCHIA)

Morphological and functional characteristics of the haemocytesof Viviparus ater were studied. Only one cell type occurs inthe haemolymph: the spreading haemocyte. These cells have thesame functions as blood cells belonging to the spreading typefound in other gastropods. It is also suggested that the spreadinghaemocytes represent the ancestral cell responsible for defencemechanisms. (Received 18 May 1988; accepted 19 August 1988)     

THE FOURTEEN SPECIES OF ZIZIPHUS INCLUDING SARCOMPHALUS (RHAMNACEAE) INDIGENOUS TO THE WEST INDIES

Taxonomic treatment is presented for the 14 species of Ziziphus P. Mill. (Rhamnaceae: Dicotyledoneae) recognized in the West Indies, with key, synonymies, and statements of distribution. New combinations include Z. crenata (Sarcomphalus crenaius Urb.), Z. microdictya (S. microdictyus Urb. & Ekm.), Z. acutifolia (S. acutifolius Griseb.), Z. bidens (S. bidens Urb.), Z. obovata (S. obovatus Urb.), Z. havanensis var. bullata (S. bullatus Urb.), and Z. taylori (S. taylori Britt.). New names include Z. urbani (S. parvifolius Urb. & Ekm.) and Z. grisebachiana (S. divaricatus Griseb.). The available evidence of evolutionary relationships is assessed.     

EFFECTS OF HEAVY METALS ON SURVIVAL AND GROWTH OF BIOMPHALARIA GLABRATA SAY (GASTROPODA: PULMONATA) AND INTERACTION WITH SCHISTOSOME INFECTION

The effects of dissolved Pb, Cd and Hg on growth and survivalof adult Biomphalaria glabrata Say. uninfected and infectedwith Schistosoma mansoni Sambon, were examined. Pb at concentrationsfrom 0.25–100 µM, Cd from 0.075–0.25 µMand Hg from 0.25–1 µM significantly reduced growthand survival of normal snails. With each metal the effects increasedwith increasing concentration. The LC 25 at 2 wks exposure was82 ± 19, 0.22 ± 0.04 and 0.94 ± 0.13 µM(x ± S.E.) for Pb, Cd and Hg, respectively. Snails exposedto heavy metals continued to be reproductively active, but theegg production was highly variable and no significant effectof heavy metal exposure was demonstrated. Infection also decreasedsurvival and growth of snail hosts and infected individualsexposed to heavy metals displayed the greatest mortality. TheLC 25 for infected snails at 2 wks exposure was 8 ± 3,0.9 ± 0.02 and 0.29 ± 0.08 for Pb, Cd and Hg respectively.A significant interaction between heavy metal exposure and infectionwas apparent. Infected snails were not reproductively active.Cercarial shedding by infected snails was significantly reducedin the presence of heavy metals and by 6 wks shedding had ceasedat the highest metal concentrations. (Received 20 May 1996; accepted 31 July 1996)     

ALLOZYME VARIATION AMONG POPULATIONS OF BIOMPHALARIA CAMERUNENSIS (BOETTGER, 1941) (GASTROPODA: PLANORBIDAE) IN CAMEROON

Allozyme electrophoresis was used to study genetic diversityamong populations of the freshwater, hermaphroditic snail Biomphalariacamerunensis in Cameroon. Five of 19 loci studied in 15 enzymesystems were polymorphic. Intrapopulation variation was evidentin 8 of 12 populations sampled and heterozygotes were presentin 6 of these. Two populations with large sampled sets werepanmictic. Although results for the remaining 4 populationswith heterozygotes present were inconclusive, our findings supportthe hypothesis that Biomphalaria are out-breeders. The allelesfor two loci, asparate aminotransferase-1 (AAT-1) and 6-phosphogluconatedehydrogenase (6-PGD), showed distribution patterns that suggestthey may be limited by climate or habitat. The slow migratingAAT-1 was the only allele found in the mountainous regions ofthe southwest. This region falls under the Cameroon-type climateand is the wettest region in the country. The faster allelewas restricted to the lowland rain forest of the south. For6-PGD the fast allele was found throughout the range of B. camerunensis,but the slower allele was found only in the mountainous regionswithin the Cameroon-type climate. (Received 27 April 1989; accepted 9 September 1989)     

ALLOZYME VARIATION AMONG POPULATIONS OF BIOMPHALARIA PFEIFFERI (KRAUSS, 1848) (GASTROPODA: PLANORBIDAE) IN CAMEROON

Allozyme electrophoresis was used to study genetic diversityamong the freshwater, hermaphroditic snail Biomphalaria pfeifferiin Cameroon. Four of 19 loci studied were polymorphic. The allozymesfor two loci, aspartate aminotransferase-1 (AAT-1) and isocitratedehydrogenase (IDH), showed distribution patterns related toclimatic zones. AAT-1¹⁰⁰ and IDH¹⁰⁰ occurred predominantly inthe Tropical Climatic Zone, located in the northern half ofthe country. AAT-1¹⁴⁰ and IDH⁹⁰ were common in the EquatorialZone. Intrapopulation variations occurred in 5 of 19 populationsampled. Only one population, polymorphic for AAT-1 locus, waspanmictic. The other 4 populations were not in Hardy-Weinbergequilibrium. The deficiency of heterozygotes in those populationsis unusual for a member of the genus Biomphalaria and may bedue to a predominance of self-fertilization. Other explanationsinclude ecological factors or the presence of segregated sub-populationsthat do not outcross. This latter hypothesis is supported bythe total absence of heterozygotes for PGM alleles. (Received 24 August 1989; accepted 14 September 1989)